Mobile data traffic is expected to exceed traffic from wired devices in the next couple of years. This emerging future will be empowered by revolutionary 5G radio network technologies with a focus on application-driven connectivity, transparently deployed over various technologies, infrastructures, users and devices to realise the vision of 'the Internet of Everything'. This book presents a roadmap of 5G, from advanced radio technologies to innovative resource management approaches and novel network architectures and system concepts. Topics covered include challenges for efficient multi-service coexistence for 5G below 6GHz; new quasi-deterministic approaches to channel modelling in millimetre-wave bands; large scale antenna systems; effects of densification and randomness of infrastructure deployment in cellular networks; wireless device-to-device (D2D) Links for machine-to-machine (M2M) communication; caching in large wireless networks; full duplexing; decoupled uplink and downlink access in heterogeneous networks; wireless networks virtualisation; and regulation, business and technology perspectives on licensed shared access (LSA) and three-tier spectrum sharing models. 5G Wireless Technologies is an essential guide to this emerging system for researchers, engineers and advanced students working in telecommunications and networking.

The objective of this book is to present, elaborate and assess, with respect to the impact of critical parameters, the most promising system concepts, architectures, and technology enablers that are expected to play a differentiator's role in the realization and adoption of 5G. To this end, 10 promising advanced technology topics are investigated in the following corresponding book chapters (Chapters 2-11), each describing a 5G innovation that is expected to transform wireless design understanding. A new era is commencing, following “technology-driven,”“user-centric,”and “Everything-as-a-Service”eras: the era of “Connectivity-as-a-Utility.”More specifically, the book chapters are organized into three thematic entities.

This chapter has provided a view of the current service and use case landscape for 5G networks. It also performs a selection among these use cases so that a flexible air interface design for spectrum below 6 GHz can be performed. Challenges for this design on link and system levels are then briefly discussed along with their research topics and the evaluation methodology for the corresponding technical components. We finally note that the design of a new air interface is heavily composed of topics requiring standardization, e.g., waveform and frame design, PHY layer procedures, transceiver processing (interference management, multiuser reception, etc.), channel coding, adaptive coding and modulation, etc. These are all topics that imply interfaces, messages, signalling, protocols (all of which are standardized in 3GPP) rather than proprietary algorithmic solutions and an important challenge for researchers is to be able to interact with standardization bodies, especially 3GPP, in a timely manner.

In this chapter, a novel quasi-deterministic modeling methodology for millimeterwave channels was proposed. The methodology is based on a number of previous experimental works and a few special measurement campaigns at 60 GHz performed during the MiWEBA project in different scenarios and environments. Since the 60 GHz band is exactly in the middle of the millimeter-wave frequency range of 30-90 GHz, the results presented in this work may be extrapolated in both directions, making the developed methodology applicable to this frequency range.

This chapter has overviewed the principles of LSAS systems, as one of the dominant candidates for 5G communication networks and beyond. It is the remarkable advantages of LSAS, promised by communications theory that form the main driver for the adoption of LSAS systems in future networks. The implementation of LSAS is however subject to severe challenges, which pose the question of whether the promised benefits can be materialised in practice, and to what extent. This has been the central stimulus for the pursuit of practical approaches for LSAS deployment. While academic and industrial research on LSAS has been gaining momentum globally, a number of research problems remain open to this day, as identified throughout this chapter, promising a fruitful research field in the years to come.

This chapter examined the effects of densification and randomness of infrastructure in future cellular networks by employing analytical tools from stochastic geometry. Various operational scenarios were investigated, including uplink and downlink transmissions, multi-tier networks, and variable traffic load, as well as parameters and metrics of interest such as SIR, user rate, degrees of freedom, and multiple access schemes. It was shown that randomness of AP positions introduces an unavoidable but moderate performance degradation compared to a regular placement pattern. Surprisingly enough, densification of randomly placed infrastructure does not (statistically) degrade performance in terms of SIR or user rate, even under the worst case scenario where all nodes are transmitting. Taking into account inactive transmitters (due to having no associated receivers), densification results in performance improvements. Performance gains were explicitly quantified with simple closed-form expressions in most cases.

Device-to-Device (D2D) communications will play an important role in the fifth generation (5G) cellular networks, by increasing the spatial reuse of spectrum resources and by enabling communication links with low latency. D2D is composed of two fundamental building blocks: proximity discovery and direct communication between nearby users. Another emerging trend in wireless cellular systems is Machine-to-Machine (M2M) communications, often characterized by fixed, low transmission rates. In this chapter we motivate the synergy between D2D and M2M, and present technologies that enable M2M-via-D2D communication to operate as an underlay to the ordinary cellular transmissions.

In this chapter we study the fundamental theoretical underpinnings of wireless networks with caching capabilities. More specifically: 1. We present an analytical tool for simplifying the calculations required to decide the optimal content replication in a wireless network. This tool is used to derive the asymptotic laws of backhaul capacity scaling for multihop wireless networks. The presented results consider (i) the number of networks nodes N, (ii) the number of contents M, and (iii) the cache size K as the key system “size”parameters that increase arbitrarily at different proportions. By studying the different cases we extract valuable intuition into the benefits of caching for the sustainability of wireless networks. 2. We investigate the performance of dense cache-enabled small cell networks and provide useful insights on how the system operating values, the network topology and the interference affect the network performance. Using tools from stochastic geometry to model the node distribution, we provide guidelines where to place the most popular content, i.e., at the mobile device or at the AP/BS. The effect of spatial correlation in content requests is also analysed. 3. The chapter is concluded with a summary of interesting research directions for the future that can play a crucial role in the proliferation of caching as a wireless network technique.

This chapter discusses the FD transceiver and system solutions for 5G wireless networks. The focus is on FD transceiver solutions for compact form factor wireless devices, such as handheld ones and small access points/base stations (e.g., femto cell). We further concentrate on FD transmission solutions in small area radio communication systems. In Section 8.2, the challenges with FD transceiver implementation and FD transmission in small area radio communication systems are introduced. The FD transceiver architecture options and transceiver solutions for compact form factor devices are discussed, including examples on implemented hardware prototypes developed in the EU FP7 research project DUPLO [21] in Section 8.3. In Section 8.4, FD system aspects and potential performance gains of using FD transmission in small area radio systems are discussed. Finally, conclusions and proposals for further work are given in Section 8.5.

This chapter describes in detail the DUDe technique. First, Section 9.2 goes through the main challenges HetNets must face in terms of radio planning and interference management, and reviews the potential solutions to address these problems. Thereupon, decoupling UL and DL is recognised as a new technique that can effectively improve the HetNet performance, as shown in Section 9.4, and also can impact positively the performance of other radio access technologies, such as Carrier Aggregation (CA), Coordinated Multipoint transmission and reception (CoMP) or millimetre wave (Section 9.5). The enabling radio access network architectures are discussed in Section 9.6 and higher layer opportunities and challenges are addressed in Section 9.7.

On the road towards 5G, virtualization is viewed as one of the critical technologies to maximize the network flexibility, scalability and efficiency in order to accommodate diverse applications and scenarios. Despite the simplicity of the idea of adopting virtualization to telecom industry, the implementation is more difficult in practice. Wireless communication is distinct from IT data centres in that wireless communication has extremely strict requirements on real-time processing. In this chapter, the virtualization on radio access networks, in particular C-RAN, is carefully studied with the analysis on the challenges and potential solutions. Given that RAN functions, such as baseband processing, require intensive computation and real-time processing, the RAN virtualization then requires joint optimization on various system modules, including the operating systems, the hypervisor, etc. It also requires enhancement and optimization on existing traditional IT technologies including the network acceleration, live migration, VM communication, support of OpenStack and so on. A prototype of optimized virtualization platform with enhanced real-time performance was developed. The tests have shown that the optimized round-trip L2 processing latency of the platform could be reduced to around 30us on average, while it is usually around 300-500us in traditional Linux system. In the meantime,the VM communication latency could be optimized to around 10us, compared to several hundred microseconds for traditional Linux system. Enhancement on the platform real-time performance is just the first step. In future, much more work should be involved such as real-time management, virtualization granularity, hardware acceleration, design of high-speed low-latency switch networks, etc. to realize completely virtualized C-RAN systems.

Spectrum sharing is an important enabler for future mobile broadband systems to meet the growing end user data traffic needs. Considering spectrum sharing from regulation, business and technology perspectives is the key for the successful development of sharing models that can be deployed in practical systems. This chapter studies recent spectrum sharing concepts from regulatory, business and technology perspectives. We present the European Licensed Shared Access (LSA) spectrum sharing concept covering its regulatory, business, and technical aspects with a focus on the LSA case example of sharing between LTE and incumbent program making and special events (PMSE) services in the 2.3-2.4 GHz band. The LSA evolution including more dynamic sharing toward the US three-tier spectrum sharing model for Citizen Broadband Radio Service (CBRS) based on Spectrum Access System (SAS) is depicted in terms of its ecosystem, business benefits, and technical approaches. Future outlook is given to envisage the development of sharing models for the mobile broadband.

Assuming success, 5G will not just introduce a new way of thinking in wireless networks design and optimization, but a new era, where “Wireless Connectivity as a Utility”will completely transform the way people, things, and (any) application devices communicate, store, and process information. As speed (data rate), data volume, distance, agility (latency), security, and reliability become “non-issues,”“infinite”capacity, and unlimited connectivity initiate an ecosystem paradigm shift, according to which network infrastructure as a whole is always available, scalable, and functioning “in the background,”whereas wireless access is ubiquitous and technology agnostic (independent). This new utility-like Quality of Experience clearly shifts the center of gravity from the network (infrastructure) side toward the user end (network edge) and from radio and networking technologies to applications.